1. Field of the Invention
The present invention relates to an antenna. More specifically, the present invention is a novel and improved pillbox antenna having beam directive lips formed at the antenna aperture and constructed for rotation about a radiating feed probe positioned at the focus of the antenna parabolic reflecting cylinder.
2. Background Art
Pillbox antennas have been known for their use in applications where a directional antenna is required. Typically, the pillbox antenna has been used in radar systems and in particular marine radar systems. This type of antenna has generally not been used in communications systems due to the directivity limitations of the antenna. The pillbox antenna, when mounted in a horizontal plane, provides a beam shape that is substantially sharper in directivity in the horizontal plane than that of the vertical plane.
A pillbox antenna is generally defined as a radiating cavity formed by a parabolic reflecting cylinder axially terminated by parallel plates. The cavity structure includes an open mouth or aperture formed at a forward portion of the cavity. Typically, a horn or outwardly extending lips are formed at the aperture. The lips extend forward from the aperture and diverge symmetrically from a common plane defined by the parallel plates while diverging on opposite sides of the common plane. This configuration of lips dictates a beam pattern that spreads out in the vertical plane when the antenna is mounted in the horizontal plane.
It is, therefore, an object of the present invention to provide a new and improved highly directional rotatable pillbox antenna and antenna assembly for telecommunication applications.